usingHuman Visual System (HVS). But the encryption technique needs cryptographiccomputation to

divide the image into a number of parts let n. k-n secret sharingscheme is a special type of Visual

Cryptographic technique where at least a groupof k shares out of n shares reveals the secret

information, less of it will reveal noinformation.

In our paper we have proposed a new k-n secret sharing scheme forcolor image where encryption

(Division) of the image is done using RandomNumber generator.

EXISTING SYSTEM:

Visual cryptography

is the art and science of encrypting the image in such a waythat no-one apartfrom the sender and intended recipient even realizes the originalimage, a form of security through obscurity. By contrast, cryptography obscuresthe original image, but it does not conceal the fact that it is not the actual image.

LIMITATIONS:-



The existing system does not provide a friendly environment to encrypt ordecrypt the data (images).



The existing system supports with only one type of image format only. Forexample, if it is .jpg, then it supports only that same kind of image formatonly.

PROPOSED SYSTEM:

Proposed systemVisual cryptography

provides a friendly environment to deal withimages. Generally cryptography tools supports only one kind of image formats.Our application supports .gif and .png (portable network graphics) formattedimages and our application has been developed using swing and applettechnologies, hence provides a friendly environment to users.

Problem Definition:

Whenever

we transmit the data (image) in the network, anyunauthenticated person can read our data (image). In order to provide security to

data (image) generally sender will encrypt the data (image) and send it the intendedperson and the receiver will decrypt the encrypted data (image) and uses it.

MODULES

:-



Interface design usingUI

frame work



Visual cryptography implementation



Encoding



Decoding



CreatingTransparencies



Un-hiding Image from Transparency



Testing and integration

MODULES DESCRIPTION:

Interface design usingUI

frame work

In this module, we design user interface design usingUI

frame work. The userinterface should be very easy and understandable to every user. So that any one canaccess using our system. It must be supportable using various GUIs. The userinterface also consists of help file. The help file assists on every concepts of theembedded visual cryptography. Help file should clearlydepict the details of theproject developed in simple language using various screen shoots.

Visual cryptography Implementation

This module is the core for the project, where we implement the VisualCryptography. We used LZW Data Compression algorithm. The

LZW datacompression algorithm is applied for the gray scale image here. As a pre-processing step, a dictionary is prepared for the gray scale image. In thisdictionary, the string replaces characters with single quotes. Calculations are doneusing dynamic Huffman coding. In compression of greyscale image select theinformation pixels. Then generate halftone shares using error diffusion method. Atlast filter process is applied for the output gray scale images. Filters are used toimprove the quality of reconstructed image to minimize the noises for sharpeningthe input secret image.

Encoding

A high level view of the encoding algorithm is shown here:

1.

Initialize the dictionary to contain all strings of length one.

2.

Find the longest string W in the dictionary

that matches the current input.

3.

Emit the dictionary index for W to output and remove W from the input.

4.

Add W followed by the next symbol in the input to the dictionary.

5.

Go to Step 2.

A dictionary is initialized to contain the single-character strings corresponding toall the possible input characters (and nothing else except the clear and stop codes ifthey're being used). The algorithm works by scanning through the input string forsuccessively longer substrings until it finds one that is not in the dictionary. Whensuch a string is found, the index for the string less the last character (i.e., thelongest substring thatis

in the dictionary) is retrieved from the dictionary and sentto output, and the new string (including the last character) is added tothedictionary with the next available code. The last input character is then used as thenext starting point to scan for substrings.

Decoding

The decoding algorithm works by reading a value from the encoded input andoutputting the corresponding string from the initialized dictionary. At the sametime it obtains the next value from the input, and adds to the dictionary theconcatenation of the string just output and the first character of the string obtainedby decoding the next input value. The decoder then proceeds to the next inputvalue (which was already read in as the "next value" in the previous pass) andrepeats the process until there is no more input, at which point the final input valueis decoded without any more additions to the dictionary.

Inthis way the decoder builds up a dictionary which is identical to that used by theencoder, and uses it to decode subsequent input values. Thus the full dictionarydoes not need be sent with the encoded data; just the initial dictionary containing

the single-character strings is sufficient (and is typically defined beforehand withinthe encoder and decoder rather than being explicitly sent with the encoded data.)

Creating Transparencies

This scheme provides theoretically perfect secrecy. An attacker whoobtains eitherthe transparency image or the screen image obtains no information at all about theencoded image since a black-white square on either image is equally likely toencode a clear or dark square in the original image. Another valuable property ofvisual cryptography is that we can create the second layer after distributing the firstlayer to produce any image we want. Given a known transparency image, we canselect a screen image by choosing the appropriate squares to produce the desiredimage. One of the most obvious limitations of using visual cryptography in the pastwas the problem of the decoded image containing an overall gray effect due to theleftover black sub pixel from encoding. This occurred because the decoded imageis not an exact preproduction, but an expansion of the original, with extra blackpixel. Black pixel in the original document remains black pixel in the decodedversion, but White pixel becomes gray. This resulted in a lot of contrast to theentire image. The extra black sub pixel in the image causes the image to becomedistorted.

D-

Secret information. K-

Number of shares generated from D. share-

piece ofinformation.

Divide data D into n pieces in such a way that D is easily reconstruct able from anyk pieces, but even complete knowledge of any k-1 pieces reveals no informationabout D. Stacking two pixels (each consists of four sub-pixels) can occur forexample the following two cases: Secret sharing scheme is a method of sharingsecret information among a group of participants. In a secret sharing scheme, eachparticipant gets a piece of secret information, called a share. When the allowedcoalitions of the participants pool their shares, they can recover the shared secret;on the other hand, any other subsets, namely

non-allowed coalitions, cannotrecover the secret image by pooling their shares. In the last decade, various secretsharing schemes were proposed, but most of them need a lot of computations todecode the shared secret information.

The basic 2 out of 2 visual cryptography model consist of secret message encodedinto two transparencies, one transparency representing the cipher text and the otheracting as a secret key. Both transparencies appear to be random dot when inspectedindividually and provide no information about the original clear text. However, bycarefully aligning the transparencies, the original secret message is reproduced.The actual decoding is accomplished by the human visual system. The original isencrypted into 2 transparencies you needboth transparencies to decode themessage.

Un-hiding Image from Transparency

The simplest form of visual cryptography separates an image into two layers sothat either layer by itself conveys no information, but when the layers arecombined the image isrevealed. One layer can be printed on a transparency, andthe other layer displayed on a monitor. When the transparency is placed on top ofthe monitor and aligned correctly, the image is revealed. For each image pixel, oneof the two encoding options is randomly selected with equal probability. Then, theappropriate colorings of the transparency and screen squares are determined basedon the color of the pixel in the image.

Testing and integration

This is the final module, which consists of integration of

Visual cryptographyimplementation module into interface design using applet viewer. Then we need totest with various images and formation of transparencies. The transparenciesshould be able to save and load into the user interface.